In general, a container 100 that contains liquid materials of oil, paint and chemical products as well as beverages such as water and milk, includes a container body 110 having a mouth, and a cap 130 that opens and closes the mouth of the container body. The cap is largely classified into a screw-coupling type or a one-touch type according to an opening and closing structure.
In the case of a screw-coupling type cap 130 shown in FIGS. 1 and 2, a female screw portion is formed on an inner circumferential surface of the cap 130 in correspondence to a bottle or container body 110 on which a male screw portion is formed on an outer circumferential surface of the mouth of the container body 110. In the case that the cap is completely separated from the container body, it may be polluted or lost. Accordingly, a fixing ring 133 for preventing the cap from being separated from the container body 110 is provided at a lower portion of cap body 131 so that the cap is maintained connected with the container body 110 when the cap is opened with respected to the container body 110.
In addition, the cap body 131 and the fixing ring 133 are connected by a plurality of bridges 135 that are radially formed. When the cap is opened, the bridges 135 are separated to then enable a user to recognize whether or not the container 100 has been opened.
Since the fixing ring 133 is combined with the container body 110 so as to retain the cap in a posture connected to the container body in the above-described conventional technology, the opened cap body 131 is connected together with the fixing ring 133, and the cap body 130 can drop downwards by dead weight at the time of pouring the container contents, or can be caught by the mouth or chin of a user. This can provide the user with a feeling of discomfort. In addition the cap can become polluted by the container contents.
In the case of a one-touch type container cap 130A shown in FIG. 3, a fixing ring 133a that is fixed to a container body and a cap body 131a that performs opening and closing operations are connected by a hinge portion 135a. 
The hinge portion 135a is formed with a relatively thin thickness, in comparison with the cap body 131a and the fixing ring 133a. A width of the hinge portion 135a that connects between the cap body 131a and the fixing ring 133a is formed in a fashion that the width becomes gradually large as it goes toward both sides of the hinge portion from the middle portion of the hinge portion in correspondence to spaces between the cap body 131a and the fixing ring 133a at the time of opening the cap of the container. Accordingly, the cap body can be stably connected with the container body at the time of opening.
However, the screw-coupling type cap having bridges according to the conventional art has a technical limit with respect to an undercut treatment and thereby makes it difficult to perform a stable connection between the cap and the container.
To solve the above problems or defects, it is an object of the present invention to provide a cap for a container, including bridges for checking whether a screw-coupling type cap is opened or not and a hinge portion where an inner concave groove is formed, thereby displaying whether the cap is opened or not, and maintaining a set opening angle of the cap body in case of opening, to thus prevent the cap body from drooping and being shaken, and thereby elastically carrying out opening and closing operations, to improve use.
To accomplish the above and other objects of the present invention, according to one aspect of the present invention, there is provided a cap for a container, the cap comprising: a fixing ring for preventing separation from a container body; a cap body for opening and closing access to the container body, where a screw portion is formed on an inner circumferential surface of the cap body; a hinge portion for connecting the fixing ring and the cap body; and a plurality of bridges formed between the cap body and the fixing ring, which are separated if the cap is opened, wherein a cutting line for extending a connection length to the cap body is formed in the fixing ring around a lower portion of a hinge portion, and wherein a concave groove, which is formed on an inside portion of the cap body and the fixing ring by an inner slider of an injection molding machine, is formed in the hinge portion in such a way that the concave groove is formed with a level difference between the cap body and ribs of the fixing ring.
A cap for a container according to the present invention includes bridges for checking whether a screw-coupling type cap is opened or not and a hinge portion where an inner concave groove is formed, thereby displaying whether the cap is opened or not, thereby enabling the stable connection of a cap body and a fixing ring, thereby maintaining a set opening angle of the cap body in case of opening, to prevent the cap body from drooping and being shaken, and thereby elastically carrying out opening and closing operations, to improve use.